Fixed-time Sliding Mode Formation Control of AUVs Based on a Disturbance Observer

In this paper,we investigate formation tracking control of autonomous underwater vehicles(AUVs)with model parameter uncertainties and external disturbances.The external disturbances due to the wind,waves,and ocean currents are combined with the model parameter uncertainties as a compound disturbance.Then a disturbance observer(DO)is introduced to estimate the compound disturbance,which can be achieved within a finite time independent of the initial estimation error.Based on a DO,a novel fixed-time sliding control scheme is developed,by which the follower vehicle can track the leader vehicle with all the states globally stabilized within a given settling time.The effectiveness and performance of the method are demonstrated by numerical simulations.

Centrifuge model tests of the formation mechanism of coarse sand debris flow

Using the self-developed visualization test apparatus, centrifuge model tests at 20 g were carried out to research the macro and microscopic formation mechanism of coarse sand debris flows. The formation mode and soil-water interaction mechanism of the debris flows were analyzed from both macroscopic and microscopic points of view respectively using high digital imaging equipment and micro-structure analysis software Geodip. The test results indicate that the forming process of debris flow mainly consists of three stages, namely the infiltration and softening stage, the overall slide stage, and debris flow stage. The essence of simulated coarse sand slope forming debris flow is that local fluidization cause slope to wholly slide. The movement of small particles forms a transient stagnant layer with increasing saturation, causing soil shear strength lost and local fluidization. When the driving force of the saturated soil exceeds the resisting force, debris flow happens on the coarse sand slope immediately.

Keyhole formation and its characteristics in laser welding mode transition

Keyhole is the most important characteristic for laser deep penetration welding, and its formation indicates the beginning of laser deep penetration welding mode. The keyhole developing process was analyzed and the keyhole formation time was calculated according to welding speed and the length of weld bead formed in the keyhole formation process. The results showed that the keyhole forms in 40 -70 ms at different rate of change of laser power. In laser deep penetration welding process, the variation of light intensity radiated by laser induced plasma can identify the keyhole formation, but it can not be used to estimate the keyhole formation time because of delay effect.

Research on the Formation Modes of Emerging Technologies Based on the Species Origin Theory

Based on the research on emerging technologies and ＂the technology species＂, this thesis tries to find out the homologous relations between emerging technology and new species. The theory of the new biology species in synthetic evolution and the modern genetics is referred in the research. The modes of forming emerging technologies are discussed through some examples of IT evolvement according to modes of the biology speciation. Finally, it is pointed out that the biology species origin theory can analogize continuously the research about the evolvement mode of every emerging technology, and the implications have been bought to enterprises based on the formation conditions of each mode.

Robust Adaptive Gain Higher Order Sliding Mode Observer Based Control-constrained Nonlinear Model Predictive Control for Spacecraft Formation Flying

This work deals with the development of a decentralized optimal control algorithm, along with a robust observer,for the relative motion control of spacecraft in leader-follower based formation. An adaptive gain higher order sliding mode observer has been proposed to estimate the velocity as well as unmeasured disturbances from the noisy position measurements.A differentiator structure containing the Lipschitz constant and Lebesgue measurable control input, is utilized for obtaining the estimates. Adaptive tuning algorithms are derived based on Lyapunov stability theory, for updating the observer gains,which will give enough flexibility in the choice of initial estimates.Moreover, it may help to cope with unexpected state jerks. The trajectory tracking problem is formulated as a finite horizon optimal control problem, which is solved online. The control constraints are incorporated by using a nonquadratic performance functional. An adaptive update law has been derived for tuning the step size in the optimization algorithm, which may help to improve the convergence speed. Moreover, it is an attractive alternative to the heuristic choice of step size for diverse operating conditions. The disturbance as well as state estimates from the higher order sliding mode observer are utilized by the plant output prediction model, which will improve the overall performance of the controller. The nonlinear dynamics defined in leader fixed Euler-Hill frame has been considered for the present work and the reference trajectories are generated using Hill-Clohessy-Wiltshire equations of unperturbed motion. The simulation results based on rigorous perturbation analysis are presented to confirm the robustness of the proposed approach.

Multi-modes control method for spacecraft formation establishment and reconfiguration near the libration points

This paper studies Multi-modes control method for libration points formation establishment and reconfiguration. Firstly, relations between optimal impulse control and Floquet modes are investigated. Method of generating modes is proposed. Characteristics of the mode coefficients stimulated at different time are also given. Studies show that coefficients of controlled modes can be classified into four types, and formation establishment and reeonfiguration can be achieved by multi-impulse control with the presented method of generating modes. Then, since libration points formation is generally unstable, mutli-modes keeping control method which can stabilize five Floquet modes simultaneously is proposed. Finally, simulation on formation establishment and reconfiguration are carried out by using method of generating modes and mutli-modes keeping control method. Results show that the proposed control method is effective and practical.

Robust Formation Maneuvers Through Sliding Mode for Multi-agent Systems With Uncertainties

This paper develops a robust control method for formation maneuvers of a multi-agent system. The multi-agent system is leader-follower-based, where the graph theory is utilized to describe the information exchange among the agents. The control method is exercised via sliding mode methodology where each agent is subjected to uncertainties. The technique of nonlinear disturbance observer is adopted in order to overcome the adverse effects of the uncertainties. Assuming that the uncertainties have an unknown bound, the formation stability conditions are investigated according to a given communication topology. In the sense of Lyapunov, not only the formation maneuvers of the multi-agent system have guaranteed stability, but the desired formations of the agents are also realized. Compared with other two control approaches, i.e., the basic sliding mode approach and the fuzzy sliding mode approach, some numerical results are presented to illustrate the effectiveness, performance and validity of the robust control method for formation maneuvers in the presence of uncertainties.

Geological Features and Reservoiring Mode of Shale Gas Reservoirs in Longmaxi Formation of the Jiaoshiba Area

This study is based on the sedimentation conditions, organic geochemistry, storage spaces, physical properties, lithology and gas content of the shale gas reservoirs in Longmaxi Formation of the Jiaoshiba area and the gas accumulation mode is summarized and then compared with that in northern America. The shale gas reservoirs in the Longmaxi Formation in Jiaoshiba have good geological conditions, great thickness of quality shales, high organic content, high gas content, good physical properties, suitable depth, good preservation conditions and good reservoir types. The quality shales at the bottom of the deep shelf are the main target interval for shale gas exploration and development. Shale gas in the Longmaxi Formation has undergone three main reservoiring stages：the early stage of hydrocarbon generation and compaction when shale gas reservoirs were first formed; the middle stage of deep burial and large-scale hydrocarbon generation, which caused the enrichment of reservoirs with shale gas; the late stage of uplift, erosion and fracture development when shale gas reservoirs were finally formed.

Diagenetic Alteration Modes of the Deep Formation of Paleogene of Chezhen Depression,Bohai Bay Basin

The deep buried clastic formation of Paleogene is an important hydrocarbon reservoir in the Chezhen depression.There are two types of diagenetic alteration modes in it.The first mode is weak compaction, strong cementation,fracturing and weak dissolution in the sandstone and conglomerate on the steep slope of the depression.The reservoirs are cemented mainly by carbonate minerals strongly。

MARK XIIA Mode V询问和应答过程研究

Mark XIIA是美军和北约盟军统一研制的新型敌我识别系统,其中Mode V IFF是Mark XIIA最为重要的部分。对Mark XIIA Mode V的工作原理和信号格式进行了分析,给出了系统工作原理框图,叙述了Mark XIIA Mode V询问信号和应答信号的产生流程,分析了Mark XIIA Morde V的设计特点。从设计上解决了现役IFF存在的主要问题。

The mechanism of unconventional hydrocarbon formation: Hydrocarbon self-sealing and intermolecular forces

The successful development of unconventional hydrocarbons has significantly increased global hydrocarbon resources, promoted the growth of global hydrocarbon production and made a great breakthrough in classical oil and gas geology. The core mechanism of conventional hydrocarbon accumulation is the preservation of hydrocarbons by trap enrichment and buoyancy, while unconventional hydrocarbons are characterized by continuous accumulation and non-buoyancy accumulation. It is revealed that the key of formation mechanism of the unconventional reservoirs is the self-sealing of hydrocarbons driven by intermolecular forces. Based on the behavior of intermolecular forces and the corresponding self-sealing, the formation mechanisms of unconventional oil and gas can be classified into three categories:(1) thick oil and bitumen, which are dominated by large molecular viscous force and condensation force;(2) tight oil and gas, shale oil and gas and coal-bed methane, which are dominated by capillary forces and molecular adsorption;and(3) gas hydrate, which is dominated by intermolecular clathration. This study discusses in detail the characteristics, boundary conditions and geological examples of self-sealing of the five types of unconventional resources, and the basic principles and mathematical characterization of intermolecular forces. This research will deepen the understanding of formation mechanisms of unconventional hydrocarbons, improve the ability to predict and evaluate unconventional oil and gas resources, and promote the development and production techniques and potential production capacity of unconventional oil and gas.

Melt film formation and disintegration during novel atomization process

Hybrid atomization is a new powder-making method and can produce economically very fine, clean, spherical tin alloy powders with average particle size about 10μm and narrow size distributions. The key concept of hybrid atomization is to control the liquid film formation on disk for fine powder production. Low-pressure gas atomization was utilized to promote the formation of a very thin stable liquid film before centrifugal breakup and give a better preparation for the final disintegration of melts. Besides the breakup ability of the rotating atomizer, the characteristics of liquid film on rotating disk affect the atomization mechanism and results remarkably. The main disintegration mode of melt is the breakup type of liquid film, which depends on the film instability and the atomization ability of the rotating disk. On the other hand, the mean powder size relates closely to the film thickness. The powder size distribution is mainly controlled by the atomization mode and the stability, flow type of liquid film on the rotating disk. A very thin, stable liquid film with long ligaments and a small pitch in LF mode results in very fine uniform tin alloy powders.

Discussion of the Mode and Mechanism of Oil and Gas Accumulation in the Nanbaxian Pool in the North of the Qaidam Basin

Because of the difference ofoil and gas accumulation condition between the hanging wall and the footwall of a fault, there is a peculiar accumulation mechanism that oil and gas mainly exists in the hanging wall of the basement fault, but in the footwall of the shallow detachment fault in the Nanbaxian pool. The oil and gas of the Nanbaxian pool came from the mature Jurassic hydrocarbon source rock of the Yibei depression located at the south of the Nanbaxian pool. Firstly, the oil and gas accumulated in the traps of the hanging wall of the basement fault by way of the unconformity and the basement faults, and turned into some primary deep pools; and then, the shallow detachment fault that formed in the later tectonic movement broke into the deep primary pools, which caused the oil and gas migration upwards along the basement faults and the shallow detachment faults and the evolvement into some secondary oil and gas pools later. The history of the Nanbaxian oil and gas accumulation can be summarized successively as the syndepositional upheaval controlled by faults; single hydrocarbon source rock; unconformities and faults as migration channels; buoyancy, overpressure and tectonic stress as dynamic forces; multistage migration and accumulation of oil and gas; and finally an overlapped double-floor pattern of oil and gas accumulation. The most important explorative targets in the north of the Qaidam Basin are traps connected with the primary pools in the footwall by shallow detachment faults.

主要国际大通道形成模式、运维经验及对中国的启示

国际大通道内涵丰富,形成模式多样,融合性强,目前学界、业界尚无统一定义;但其在全球化持续深入背景下,对国家、地区乃至全球发展的基础性、战略性作用日益突出。马六甲海峡、苏伊士运河等主要国际大通道的稳定发展,得益于相关政府的科学规划、协同联动,以及企业主体的国际化运作和绿色、数字实践等。我国对现代国际大通道的建设、研究等起步晚、基础弱,应深入研究国际大通道发展情况,借鉴相关国家政府、企业的经验做法,提升国际大通道建设、维护和把控能力,充分利用国际大通道促进高水平对外开放,推动共建“一带一路”高质量发展,保障我国全球利益和发展安全,推动构建国内国际双循环新发展格局。

人才高地的演化与形成机理研究:基于硅谷、特拉维夫、中关村、筑波的纵向案例分析

人才高地是世界重要人才中心和创新高地的战略擎画,也是实施新时代人才强国战略的内在要求。在构建“动因-过程-结果”逻辑框架的基础上,选取硅谷、特拉维夫、中关村、筑波进行纵向多案例研究,探讨人才高地的演化与形成过程。研究发现:(1)人才高地演化过程是由初始阶段、发展阶段、成熟阶段构成,经历了竞争优势驱动、政府干预驱动、价值最优驱动的动态更迭;(2)人才高地形成机理显现为资源聚合机理、资源整合机理、资源耦合机理的有序推进,体现出关键科创人才“开发者→架构者→引领者”的演变趋势;(3)人才高地实现了由低阶到高阶的“点状结构-线状结构-网状结构”的递进演化,表现为自发迭代型生成模式、创业延伸型生成模式、生态拓展型生成模式、科研深耕型生成模式等差异化类型。研究结果是构建了人才高地的演化过程理论模型,挖掘了人才高地的过程、机理和模式,以期为建设人才高地和人才平台提供有益借鉴。

大学班级管理“雁阵”模式探究

班级管理是大学教育中不可或缺的一部分,对于培养学生的综合素质和推动学校整体发展具有重要意义。近年来,“雁阵”模式作为一种以团队合作为核心的管理模式备受推崇。因此,文章通过对“雁阵”模式的理论阐述,结合大学班级管理的实际情况,试将其应于大学班级管理中,以推动学生干部队伍优化升级,助推高校班级管理制度的有效实施,进而实现大学班集体积极健康发展,最终实现大学生全面发展。

四川盆地下寒武统筇竹寺组海相页岩气高产井突破与富集模式

多年来下寒武统筇竹寺组页岩气勘探开发进展缓慢,资201井获高产气流大大增加了该套页岩气规模商业化开发的信心,不同区域及层段富集规律差异及下一步勘探开发方向是筇竹寺组页岩开发面临的首要问题。以四川盆地57口钻井资料为基础,对多口重点井的古生物、沉积、储层等特征进行分析,详细剖析资201井的部署理论依据、筇竹寺组页岩气富集条件及下一步勘探开发方向。从地层研究入手,建立了筇竹寺组地层划分标准,明确筇竹寺组主体发育4套深水陆棚相的富有机质页岩(①至④号层段),其分布受裂陷槽发育控制,裂陷槽内厚度最大。分析了页岩储层发育特征,指出储层压力、孔隙度、含气饱和度从下向上、从裂陷槽外到内呈现增大趋势,储层超压对页岩孔隙保存起到重要作用;基于此结合保存条件等建立了“多层异相、超压保孔”的页岩气超压差异富集模式,指出远离散失通道的超压孔隙发育区(层段)是页岩气富集有利区(层段)。文章指出资201井及周边是未来筇竹寺组页岩气增储上产的主要区域,资源量为8.06×10^(12)m^(3);川西地区具有相当的开发潜力,资源量为0.72×10^(12)m^(3);川南长宁及黔北一带受石墨化及构造活动影响,以寻找远离风化壳及地表露头的超压孔隙发育区为主。

济阳坳陷古生界潜山油气成藏新认识与攻关方向

古生界潜山是济阳坳陷油气富集的高产领域之一,也是重要的储量拓展阵地。古生界潜山油气成藏具有独特的石油地质条件,其地层时代老,岩性包括碳酸盐岩和碎屑岩,在漫长的地质演化过程中多期构造、断裂及深部流体活动强烈,导致潜山具有演化叠合性、结构多样性、储层复杂性、油气多源性、成藏差异性等特点。基于“十三五”以来济阳坳陷古生界潜山油气勘探进展和深化研究,从成山、成烃、成储及成藏的内在地质过程出发,揭示断陷盆地古生界潜山油气形成与富集规律,提出了“挤压-拉张-走滑-剥蚀”共控成山机制,古生界潜山具有古近系、石炭系—二叠系双源供烃条件,“沉积-成岩环境、构造-压力耦合、流体-岩石作用”三元控储模式,运移和封堵控制的油气成藏模式以及油藏有序分布规律。以这些认识为指导,实现了济阳坳陷古生界潜山油气藏勘探方向的转变,拓展了潜山勘探空间,为古生界潜山勘探区带评价及圈闭目标优选奠定了基础,并在斜坡部位和负向构造带的隐蔽潜山勘探取得突破。同时基于济阳坳陷古生界潜山不同成藏条件的认识程度和理论发展现状,提出下一步油气勘探攻关方向。

面向海流扰动和通信时延的欠驱动AUV编队跟踪控制

由欠驱动自主水下航行器(Autonomous Underwater Vehicle,AUV)编队组成的水下探测阵列具有响应快、机动性好、智能化程度高的特点。针对无速度信息传输的多AUV在海流和时延复合扰动下的编队控制问题,提出一种虚拟轨迹、轨迹预测、自适应反演滑模控制技术相结合的编队控制方法。使用领航者的位置信息和期望队形得到跟随者的参考轨迹,并引入虚拟轨迹使其与跟随者参考轨迹有限时间重合,从而得到跟随者的期望位置和速度。在此基础上,使用最小二乘法拟合轨迹曲线进行时延补偿,并通过自适应反演滑模控制技术完成海流干扰下的编队轨迹跟踪。理论分析和仿真结果表明,新方法具有可行性和有效性。

松辽盆地营城组火山岩相发育特征——以吉林省九台地区野外露头为例

为了解松辽盆地营城组火山岩类型、火山岩相类型及成因模式的复杂性、相关性之间的关系,明确其对于油气勘探的意义,利用野外露头、钻井资料、岩石薄片等多种地质资料,识别火山岩类型,划分火山岩相,分析了火山岩相成因特征。结果表明:①营城组发育4大类火山岩类型,即熔岩、火山碎屑熔岩、火山碎屑岩及碎屑沉积岩;②营城组野外露头划分了5种岩相类型,即火山口—火山通道型、火山口—破火山口型,近火山口—火山斜坡型、火山斜坡型和火山穹窿型;③建立了2类火山岩相成因模式,火山口堆积成因模式和火山斜坡成因模式。